1. Field of the Invention
The present invention relates to an image forming apparatus including a belt and a mechanism for releasing a tension provided to the belt.
2. Description of the Related Art
An image forming apparatus including a belt, such as a transfer belt, is provided, depending on the construction of the apparatus, with a mechanism of providing a pressure by a pressurization mechanism. The belt is often formed by an elastic material such as rubber or plastics. The pressurized member of such elastic material, when let to stand over a time, may require a time for recovery from a deformed state or may remain in the deformed state, depending on pressure and atmospheric conditions such as temperature and humidity. Such deformation may cause problems such as an image defect or a conveying failure.
In general, the product such as an image forming apparatus is so designed as not to easily cause such problems under certified conditions of operation, but during transportation or storage in the course of circulation of the product, it may be let to stand over a time under an environment exceeding the certified conditions of operation. In order to guarantee the quality of the product even in such situation, there is known a method of releasing the pressurization by the pressurization mechanism only during the delivery from the forwarding of the product to the installation thereof.
Following is known as background technology. In a commonly employed constitution, an exclusive pressure releasing member is mounted, at the forwarding of the product, to release the pressurization by the pressurization mechanism, and, at the installation thereof, the pressure releasing member is removed by the user to restore the pressurization by the pressurization mechanism. More specifically, FIGS. 10A and 10B illustrate a conventional construction for releasing the pressurization by the pressurization mechanism for an intermediate transfer belt. A tension roller 91 is slidably supported, at both ends thereof, by elongated holes 96a, 97a formed in unit frames 96, 97, and provides the intermediate transfer belt 90 with a tension, by the functions of tension levers 92, 93 and tension springs 94, 95. At the forwarding of the product, tension releasing pieces 99 are inserted into the elongated holes 96a, 97a formed of the unit frames 96, 97, thereby forcedly retract the tension roller 91 and releasing the tension of the intermediate transfer belt 90. Then, at the installation of the product, the user extracts the tension releasing pieces 99 according to the installation procedure, whereby the intermediate transfer belt 90 is given a tension by the tension roller 91 and is pressurized again.
However, such constitution requires that the user executes the extracting operation of the tension releasing pieces 99, and there is also a concern for an accident caused by a forgotten extracting operation.